Electrohydraulic actuators are known that comprise a body defining a cylindrical cavity in which a piston slides in leaktight manner and divides the inside of the cavity into two chambers. The piston is associated with at least one rod that passes through one of the end walls of the body. The actuator also includes a bidirectional pump that is actuated by an electric motor and that includes two ports, each connected to a respective one of the chambers of the cylinder. The pump serves to transfer fluid from one chamber to the other so as to cause the piston, and thus the rod, to move, with the quantity of fluid corresponding to the volume difference between the chambers being supplied or absorbed by a compensation member, e.g. an accumulator.
Such electrohydraulic actuators are generally relatively bulky since the electric motor and the pump are located beside the cylinder.
For example, document FR 2 831 226 discloses elongate electrohydraulic actuators in which the motor, the pump, and the accumulator are placed in line with the cylinder. Ducts pierced through the walls of the cylinder enable the ports of the pump to be connected to both chambers.
Document U.S. Pat. No. 2,918,795 also discloses an electrohydraulic actuator in which the pump and the motor are provided within the piston of the actuator, each of the ports of the chamber opening out directly into a respective one of the chambers of the actuator. That arrangement is very compact, but the motor is completely immersed, and if it fails it is difficult to replace since it is necessary to disassemble the actuator entirely.